限制使用PHP进行cron作业

Question

I have a Cron Job with PHP which I want to set up on my webhost, but at the moment the script takes about 20 seconds to run with only 3 users data being refreshed. If I get a 1000 users - gonna take ages. Is there an alternative to Cron Job? Will my web host let me run a cron job which takes, for example, 10 minutes to run?

Answer 1

A cron job shouldn't have any bearing on how long it's 'job' takes to complete. If you're jobs are taking 20 seconds to complete, it's PHP's fault, not cronjob.

Will my web host let me run a cron job which takes, for example, 10 minutes to run?

Ask your webhost.

If you want to learn about optimizing php scripts, take a look at Profiling PHP Code .

Answer 2

Your cron job can be as long as you want.

The main problem for you is that you must ensure the next cron job execution is not occuring while the first one is still running . You have a lot of solutions to avoid it, basically use a semaphore.

It can be a lock file, a record in database. Your cron job should check if the previous one is finished or not. A good thing is maybe sending you an email if he cannot run because of a long previous job (this way you'll have some notice alerting you that something is maybe getting wrong) By default cron jobs with bad error dstatus on exit are outputing all the standard output to the email of the account running the job, depending on how is configured the platform you could use this behavior or build an smtp connexion on the job (or store the alert in a database table).

If you want some alternatives to cron jobs you should have a look at work queues . You can mix work queues with a cron job, or use work queue in apache-php envirronment, lot of solutions, but the main idea is to make on single queue of things that should be done, and execute them one after the other (but be careful, if you handle theses tasks very slowly you'll get a big fat waiting queue).